Do Internal Walls Need Insulation

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By DebraB

Are you wondering if internal walls need insulation?

This comprehensive article explores the importance of insulation, the various types available, and the benefits of insulating internal walls.

From batt/blanket insulation to spray foam insulation, we discuss the different options and factors to consider before insulating.

Learn about how insulation is installed in internal walls, signs that indicate the need for insulation, and common mistakes to avoid.

Stay tuned to learn all about insulating internal walls!

What Is Insulation?

Insulation is a material or a combination of materials that is used to prevent heat, sound, or electricity from being transmitted from one area to another, making it a critical component in enhancing thermal efficiency and energy efficiency in buildings.

Insulation plays a crucial role in maintaining a comfortable indoor environment by minimising heat transfer through the building envelope. It helps in reducing energy consumption by regulating the temperature inside a space, resulting in lower heating and cooling costs.

Insulation materials such as fibreglass, cellulose, foam boards, and spray foam are commonly used to provide thermal resistance and improve energy efficiency. Each material has its unique properties that contribute to the overall effectiveness of insulation in a building.

Residential and commercial properties benefit immensely from well-insulated structures, as they not only ensure a cozy living or working environment but also help in achieving sustainability goals by reducing carbon footprints.

Discover: How Long Does External Wall Insulation Last

Why Is Insulation Important?

Insulation is important because it significantly contributes to thermal efficiency, reducing energy costs and improving indoor air quality by controlling moisture levels within buildings.

By creating a barrier between the interior and exterior environments, insulation prevents heat loss or gain, leading to a more stable indoor temperature throughout the year. This stability not only enhances comfort for occupants but also reduces the demand for heating and cooling systems, resulting in decreased energy consumption and lower utility bills over time.

What Are The Types Of Insulation?

There are several types of insulation materials available, each offering unique thermal performance characteristics and U values, which measure their effectiveness in reducing heat transfer.

Batt/Blanket Insulation

Batt and blanket insulation, commonly made from mineral wool or fiberglass, are among the most widely used types of insulation due to their ease of installation and cost-effectiveness.

They come in pre-cut panels or rolls, making them convenient for handling and fitting into various spaces. Batt insulation is typically used in walls, while blanket insulation is more common in lofts and floors. Both types provide excellent thermal resistance and can help reduce energy costs. They are versatile and can be easily cut to fit around obstacles such as electrical wiring or plumbing. Their flexibility allows for a snug fit, minimising air leakage and maximising energy efficiency.

Loose-Fill Insulation

Loose-fill insulation, often made from eco-insulation materials like cellulose or fiberglass, is ideal for filling irregular spaces and providing effective thermal insulation.

One of the significant advantages of loose-fill insulation is its remarkable ability to conform to any space, making it perfect for insulating areas that are hard to reach with traditional insulation materials. Due to its loose and lightweight nature, it can be easily installed in lofts, wall cavities, and crawl spaces without causing damage to existing structures.

What sets loose-fill insulation apart is its eco-friendly properties. Made from recycled materials, such as newspaper or denim scraps, it is a sustainable option that helps reduce landfill waste and conserves natural resources.

This type of insulation is commonly used in areas where traditional insulation methods may not be practical, such as older homes with unique architectural designs or irregularly shaped spaces. Its ability to adapt to different shapes and sizes allows for seamless coverage that minimises thermal bridging and enhances energy efficiency.

Rigid Board Insulation

Rigid board insulation, including products from manufacturers like Celotex and Kingspan, offers exceptional thermal performance due to its high U value and durability.

Rigid board insulation is composed of materials such as extruded polystyrene (XPS), expanded polystyrene (EPS), or polyisocyanurate (PIR), which contribute to its impressive thermal resistance capabilities.

The structural strength of rigid board insulation makes it ideal for various applications, including roofing, wall sheathing, and foundation insulation.

This type of insulation is relatively easy to install, either by mechanical fastening, adhesive application, or as part of a sandwich panel system, making it a popular choice among builders and homeowners alike.

Spray Foam Insulation

Spray foam insulation is renowned for its ability to provide superior airtightness and moisture control, making it an excellent choice for both new construction and retrofits.

Because of its expanding nature, spray foam insulation can fill even the smallest crevices and gaps, effectively preventing air leakage and reducing energy costs. This versatility allows it to be applied to various areas, such as lofts, walls, and crawl spaces, providing a comprehensive insulation solution for a property.

Plus its insulating properties, spray foam insulation also acts as a barrier against moisture infiltration, helping to prevent mould and mildew growth.

Reflective Insulation

Reflective insulation, also known as a radiant barrier, enhances thermal efficiency by reflecting radiant heat away from living spaces, making it particularly effective in hot climates.

When radiant heat from the sun hits the roof of a building, reflective insulation bounces it back, preventing it from entering the interior and keeping the space cooler. This can significantly reduce the need for air conditioning and lower energy costs. Reflective insulation is commonly used in lofts, walls, and roofs to create a thermal barrier against heat transfer. It can be installed in new construction or retrofitted in existing buildings, offering a versatile solution for energy efficiency. The materials used in reflective insulation often consist of a layer of aluminium or metallised film on a substrate like foam or bubble wrap, providing a lightweight and durable option. Proper installation is crucial to ensure maximum effectiveness, with considerations such as proper sealing of seams and gaps to eliminate thermal bridging.

Do Internal Walls Need Insulation?

Insulating internal walls can greatly improve a building’s overall energy efficiency, comply with building regulations, and enhance comfort by reducing heat transfer between rooms.

One of the key benefits of internal wall insulation is the enhanced thermal comfort it provides. By preventing heat from escaping through walls, it helps maintain a consistent and comfortable temperature throughout the building, reducing the need for excessive heating or cooling. Internal wall insulation can also help in reducing noise transmission between rooms, providing a quieter and more peaceful indoor environment.

What Are The Benefits Of Insulating Internal Walls?

Insulating internal walls offers several benefits, including improved thermal performance, lower U values, better moisture control, and reduced energy costs.

Enhanced thermal performance through internal wall insulation brings about a significant improvement in energy efficiency by reducing heat loss or gain. This means that in colder months, heat is retained within the building, while in warmer months, it helps to keep the interior space cool. Maintaining indoor humidity levels becomes more stable with the insulation, creating a comfortable living or working environment, especially in areas with fluctuating weather conditions.

The impact of internal wall insulation extends to various types of buildings. In residential homes, it results in cosy living spaces all year round, regardless of external temperatures. Commercial buildings, enable efficient climate control, ensuring a productive and comfortable work environment for occupants. In historic or older structures, incorporating internal wall insulation helps preserve the building’s original architecture while enhancing its energy efficiency and reducing running costs.

What Are The Factors To Consider Before Insulating Internal Walls?

Before insulating internal walls, it’s crucial to consider several factors such as potential air leakage, initial and long-term costs, the risk of dampness, and the suitability of different insulation materials.

Air leakage can significantly impact the effectiveness of insulation, leading to energy wastage and reduced thermal comfort indoors. Proper sealing of gaps and cracks is essential to prevent this. Different insulation methods come with varying cost implications – while traditional materials like fibreglass may have lower upfront costs, newer options like spray foam can provide better long-term savings due to their higher insulation efficiency.

  • The importance of addressing damp issues cannot be overstated, as dampness can not only compromise the structural integrity of walls but also create health hazards due to mould growth. Effective insulation materials should have properties that resist moisture penetration.
Cellulose: Made from recycled materials, fire-resistant, and provides good soundproofing.Can settle over time and may need additional treatment to resist pests.
Spray Foam: High insulation value, fills gaps effectively, and resists moisture.Costlier upfront, potential off-gassing during installation.
Rigid Foam Boards: Easy to install, good thermal resistance.Can be more expensive, and not as environmentally friendly.


The local climate plays a significant role in determining the thermal efficiency and moisture control needs for internal wall insulation.

For instance, in colder climates where winters are harsh, higher R-values are crucial to prevent heat loss and maintain indoor comfort levels. This means that materials with excellent insulating properties like fibreglass batts, cellulose, or spray foam insulation are commonly used.

On the other hand, in warmer regions with high humidity levels, the focus shifts towards moisture control to prevent mould and mildew growth. Ventilation systems, vapour barriers, and proper sealing techniques are essential to manage moisture effectively and maintain a healthy indoor environment.

Building Materials

The type of building materials used, such as solid wall constructions or plasterboard, significantly influences the choice of internal insulation materials and methods.

When choosing natural materials for insulation, such as wool or cork, one can enhance the energy efficiency of a building while minimising environmental impact. These materials offer excellent thermal properties and can regulate humidity levels effectively.

In the case of solid wall constructions, special attention must be paid to the thickness and airflow resistance of the insulation to prevent dampness and mold growth. Cavity wall constructions, on the other hand, allow for more flexibility in insulation choices, offering improved thermal performance.


The cost of insulating internal walls can vary widely depending on factors like fibreglass, foam board, or mineral wool may come at a premium but offer superior thermal performance. Installation labour is another key cost component to consider, as professional installation ensures proper placement and effectiveness of the insulation.

While these expenses can add up, it’s essential to factor in potential savings from grants or energy efficiency incentives which can significantly offset the upfront costs.

How Is Insulation Installed In Internal Walls?

Installing insulation in internal walls involves several methods, including using battens, constructing a stud wall, or employing the warm batten technique, often accompanied by a vapour barrier to control moisture.

When considering battens, ensure they are fixed at appropriate intervals for proper support. When constructing a stud wall, remember to leave gaps for insulation insertion. For the warm batten technique, follow manufacturer instructions meticulously to achieve optimal thermal performance. In all cases, integrating a vapour barrier is crucial to minimise the risk of condensation and mould growth within the wall cavity, thus enhancing the overall efficiency of the insulation. Attention to detail during the installation process directly impacts the insulation’s effectiveness in regulating indoor temperatures and reducing energy costs.

What Are The Signs That Internal Walls Need Insulation?

Indicators that your internal walls may need insulation include poor thermal performance, noticeable air leakage, moisture damage, and rising energy costs.

One common symptom of inadequate insulation is the presence of cold spots in various rooms, where you can feel a distinct chill that doesn’t match the rest of the space. If you experience significant drafts near windows or doors, this could be a sign that your insulation is not effectively stopping outside air from entering. Another indication to watch out for is high humidity levels within your home, which can be a result of insufficient insulation causing condensation and moisture build-up.

The impact of poor insulation goes beyond just discomfort, as it can also lead to increased energy bills due to the continuous need for heating or cooling to maintain a comfortable environment. This not only adds financial strain but also contributes to unnecessary energy consumption. To address these issues, assessments such as energy audits or professional insulation evaluations can help determine the extent of your insulation needs and identify areas for improvement.

What Are The Common Mistakes When Insulating Internal Walls?

Common mistakes when insulating internal walls include improper installation, neglecting airtightness, failing to account for the dew point, and not using appropriate safety equipment.

Improper installation is a significant issue that can lead to a range of problems, such as inadequate thermal performance and moisture infiltration. When insulation is not correctly installed, gaps and voids can form, allowing heat to escape and dampness to enter. This can result in increased energy bills, uncomfortable indoor temperatures, and even structural damage over time. Ensuring a proper installation by following manufacturer instructions and utilising skilled labor is crucial for the success of the project.